Few circulating cells shed by tumours end up in the bloodstream, which makes them very difficult to find. Credit: Alfred Pasieka/Science Photo Library.
Flow cytometry has long enabled basic and clinical research, with applications in fields as diverse as molecular biology, neuroscience and plant and marine biology. Recently, its use in cancer immunology has grown impressively, because of the role it can play in extending our understanding of the immune system and its response to cancer immunotherapies. As the capabilities and precision of the analytical platforms continue to improve, so too will their beneficial effect on immunology and cancer research communities. For a decades-old analytical technique, the best, it seems, is yet to come.
Creating technology through teamwork
Most advances in flow cytometry have depended on co-creation, with scientists, research institutions and companies working together. In 1953, American electrical engineer Wallace Coulter received a patent for the Coulter Principle, a technique for analyzing particles in a fluid. In the 1970s, the combined work of the late, Stanford-based immunologist, Len Herzenberg, and Becton, Dickinson and Company (BD) turned flow cytometry into a commercial platform — the FACS-1 (fluorescence activated cell sorting). In the late 1970s, scientists at Los Alamos National Laboratories added multi-parameter capabilities to flow cytometry.
Combining that technology with the ability to manufacture fluorescent-labeled monoclonal antibodies created what Robert Balderas, vice president of biological sciences at BD Biosciences calls “one of the most amazing examples of co-creation from any industry”. Utilizing those antibodies to interrogate cancer cells, scientists dug into the disease and ways to treat it, starting with flow-cytometry platforms based on one laser and the ability to track two colours. As the technology expanded, so did the capabilities of cancer research, “Now, we build 10-laser instruments and follow 30 colours in research platforms, such as the BD FACSymphony with unprecedented access to 50 different parameters on a single cell,” Balderas explains.
The BD FACSymphonyTM system is a novel cell analyzer that leverages the benefits of flow cytometry and enables the simultaneous measurement of up to 50 different characteristics of a single cell.
Using technology to combat cancer
As flow cytometers become more sophisticated and biologists better understand cancer markers, the cells can be divided into increasingly specific groups that require progressively higher number of parameters. “The ability to decipher the complexity of cancer cells, stromal cells and tumour-infiltrating lymphocytes gives us information about solid-tissue cancers. This has been done around the world for the past 25 or 30 years in combination with oncologists and flow-cytometry platforms,” Balderas says. “Today, we’re moving into minimal residual disease (MRD) and we can find that rare cell.”
In 2006, the European Scientific Foundation for Laboratory HematoOncology launched the EuroFlow Consortium. “This major initiative is bringing consensus to the phenotypic markers that should be tested for all bloodborne cancers,” says Balderas. “But consensus is difficult, and it takes time.” The EuroFlow experts focus on developing fast, accurate and very sensitive methods of testing samples with flow cytometry.
At the University of Pennsylvania’s Perelman School of Medicine, immunologist, Erica Carpenter, and her colleagues used flow cytometry in search of circulating tumour cells (CTCs)1. Tumours shed these cells, but few of them end up in the bloodstream, which makes them extremely difficult to find. But, CTCs could be used to measure cancer at the smallest levels, leading to early treatment of new and recurring cancers.
Robert Balderas, Vice president of biological sciences at Becton, Dickinson and Company
Carpenter’s team isolated CTCs with flow cytometry and then analyzed the messenger RNA transcribed by the cells. With this system, the scientists could find one CTC in a million white blood cells. Then, the cells were divided based on gene expression. Carpenter and her colleagues concluded: “This approach is relevant in the era of immunological therapies such as chimeric antigen receptor T-cell (CAR-T) therapy.” CTCs could be captured from a patient and used as targets for developing personalized cancer therapy.
Continuing advances in flow cytometry, such as those from EuroFlow and Carpenter’s work, will reveal even more molecular details of disease, as well as ways to treat them. As Balderas says, “A patient is at the end of everything that we do.”
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